1. Field of the Invention
This invention relates to concealed fasteners for roof and wall structures, and more particularly to a panel mounted clip assembly used at the joints between adjacent panel members and at the intermediate ribs of each panel member, to secure the panel members to panel support members.
2. Description of the Prior Art
Roof structures are known wherein a plurality of panel members are erected in side-by-side relation and secured to panel support members. Adjacent panel members are connected by interlocking marginal edges to form joints. The joints may be self-closing or may be closed by seaming devices. The prior art discloses many types of concealed fastening devices which interfit with the joints and secure the panel members to the panel support members.
One-piece clips are known which are rigidly secured to the panel support member and which are interfitted with the marginal edges of adjacent panel members at the joints, see for example U.S. Pat. No. 3,982,373 (WILSON et al).
Two-piece clips are known which comprise a base member, a top member, and a slideable connection therebetween allowing the top member to move with the panels during thermal expansion and contraction thereof. In one two-piece clip, the slideable connection resides within the interfitted marginal edges of the panel members, see U.S. Pat. No. 3,858,373 (DAY et al). In another two-piece clip, the slideable connection resides below the interfitting marginal edges of the panels. The top portion of the two-piece clip may be bent resiliently to some extent laterally of the base member. The lateral bending of the top portion appears to be an attempt to accommodate slight misalignment of the interfitted marginal edges of the panels relative to the base member. Such a two-piece clip is disclosed in U.S. Pat. Nos. 4,193,247 and 4,213,282 issued to HECKELSBERG.
Prior art two-piece clips have been used at the panel joints. The panel members have limited cover widths, e.g., 24 inches or less. Most panel members are made by roll-forming operations to established finite tolerances. Where the finite tolerances are not maintained or, conversely, where the two-piece clips are not erected in precise spaced-apart relation, the panel joints are not readily alignable with the two-piece clips. The joint-to-clip misalignment may reduce the hold-down capacity of the clips and may introduce undesirable stresses which could degrade the weather-tightness of the joint and hinder the thermal expansion and contraction of the panel members.